State detection of bond wires in IGBT modules using eddy current pulsed thermography

Insulated gate bipolar transistor (IGBT) modules are important safety critical components in electrical power systems. Bond wire lift-off, a plastic deformation between wire bond and adjacent layers of a device caused by repeated power/thermal cycles, is the most common failure mechanism in IGBT modules. For the early detection and characterization of such failures, it is important to constantly detect or monitor the health state of IGBT modules, and the state of bond wires in particular. This paper introduces eddy current pulsed thermography (ECPT), a nondestructive evaluation technique, for the state detection and characterization of bond wire lift-off in IGBT modules. After the introduction of the experimental ECPT system, numerical simulation work is reported. The presented simulations are based on the 3-D electromagnetic-thermal coupling finite-element method and analyze transient temperature distribution within the bond wires. This paper illustrates the thermal patterns of bond wires using inductive heating with different wire statuses (lifted-off or well bonded) under two excitation conditions: nonuniform and uniform magnetic field excitations. Experimental results show that uniform excitation of healthy bonding wires, using a Helmholtz coil, provides the same eddy currents on each, while different eddy currents are seen on faulty wires. Both experimental and numerical results show that ECPT can be used for the detection and characterization of bond wires in power semiconductors through the analysis of the transient heating patterns of the wires. The main impact of this paper is that it is the first time electromagnetic induction thermography, so-called ECPT, has been employed on power/electronic devices. Because of its capability of contactless inspection of multiple wires in a single pass, and as such it opens a wide field of investigation in power/electronic devices for failure detection, performance characterization, and health monitoring

A method to monitor IGBT module bond wire failure using on-state voltage separation strategy

On-state voltage is an important thermal parameter for insulated gate bipolar transistor (IGBT) modules. It is employed widely to predict failure in IGBT module bond wires. However, due to restrictions in work environments and measurement methods, it is difficult to ensure the measurement accuracy for the on-state voltage under practical working conditions. To address this problem, an on-state voltage separation strategy is proposed for the IGBT modules with respect to the influence of collector current (Ic) and junction temperature (Tj). This method involves the separation of the on-state voltage into a dependent part and two independent parts during the IGBT module bond wire prediction. Based on the proposed separation strategy, the independent parts in the failure prediction can be removed, making it possible to directly monitor the voltage variations caused by bond wire failure. The experimental results demonstrate that the proposed diagnosis strategy can accurately predict the bond wire failure stage in an IGBT module under different conditions

A road map for reliable power electronics for more electric aircraft

The gradual evolution from hydro-pneumatic to electrical disposition of power in aircraft has placed stringent requirements on the reliability of power electronic components in current and future aerospace applications. This paper examines the prevalent state-of-the-art in power electronics and provides an analytical overview of power electronics in More Electric Aircraft (MEA) vis-à-vis the generation and distribution of power within these aircraft. The types of power devices currently employed for multiple conversion topologies are analysed and weighed according to their respective reliability characteristics. Beginning with an in-depth review of failure modes in the currently available devices, the paper highlights the salient emerging state-of-the-art Wide Band Gap (WBG) technologies such as Gallium Nitride (GaN) and Silicon Carbide (SiC) and draws an extensive comparison with their Silicon counterparts. A comprehensive examination of techniques employed for the estimation of the reliability of WBG power devices has revealed a number of areas that merit due consideration. For instance, the physics-based models that have been developed to assess the operational lifetime of silicon-based devices for given failure modes require revamping in light of the new materials and the unique electrical and physical characteristics the WBG devices possess. Similarly, the condition monitoring techniques, with respect to the primary and secondary parameters, require further investigation to determine highly representative feature vectors that best describe the degradation within these devices. More significantly, optimisation of the proposed techniques for the health assessment of these devices needs to be pursued through the optimal use of vital parameters. Keeping these critical findings in perspective, a road map highlighting various avenues for power electronics optimisation in MEA is put forth to apprise the aerospace fraternity of its growing significance

Characterization of high-voltage IGBT module degradations under PWM power cycling test at high ambient temperature

International audienc

Evaluation de la fiabilité d'un générateur à rayons X pour application médicale

Medical imaging systems, mainly X-rays imaging systems, have become essential in the diagnosis and treatment of complex diseases. X-rays generator is one of the critical subsystems of a medical system. Its technology became more complex and constraints seen by the components increase. An assessment of X-rays generator reliability is therefore necessary to optimize its lifetime. In this thesis, a reliability assessment method of an X-rays generator is proposed. The methodology is based on the assessment of the reliability from component to system. Aging tests are first performed for X-rays generator critical components in order to identify failure mechanisms and build lifetime curves for performing reliability prediction. FIDES guide parameters were also used to construct critical components lifetime curves. A reliability prediction method based on the assumption of cumulative damage with Miner's rule is proposed to evaluate critical components lifetime under thermomechanical stresses. This method uses rainflow counting rules for the temperature cycles distribution of critical components. A reliability block diagram is finally used to estimate the lifetime of each X-ray generator subsystem through its critical components.Les systèmes d’imagerie médicale, principalement les systèmes à rayons X, sont devenus incontournables dans le diagnostic et le traitement des maladies complexes. Le générateur à rayons X fait partie des sous-systèmes critiques d’un système à rayons X. La technologie des générateurs à rayons X se complexifie et les contraintes vues par les composants augmentent. L’évaluation de la fiabilité du générateur à rayons X est par conséquent nécessaire afin d’optimiser la durée de vie de ce dernier. Dans ces travaux de thèse, une méthodologie d’évaluation de la fiabilité d’un générateur à rayons X est proposée. La méthodologie repose sur l’évaluation de la fiabilité allant du composant au système. Des essais de vieillissement sont d’abord réalisés au niveau des composants critiques du générateur afin d’identifier les mécanismes de défaillance et de construire les courbes de durée de vie permettant d’effectuer une prévision de fiabilité. Les paramètres du recueil de fiabilité FIDES ont aussi été utilisés pour construire les courbes de durée de vie des composants critiques. Une méthode de prévision de la fiabilité basée sur l’hypothèse du dommage cumulé avec la règle de Miner est proposée pour évaluer la durée de vie des composants critiques sous contraintes thermomécaniques. Cette méthode utilise les règles de comptage rainflow pour obtenir une distribution des différences de température vues par les composants critiques. Une association de fiabilité permet enfin d’estimer la durée de vie de chaque sous système du générateur à rayons X à travers ses composants critiques

Thermal characterisation and reliability analysis of power electronic devices in wind and solar energy systems

Power electronic converters (PECs) are used for conditioning the flow of energy between renewable energy applications and grid or stand-alone connected loads. Insulated gate bipolar transistors (IGBTs) are critical components used as switching devices in PECs. IGBTs are multi-layered devices made of different coefficient of thermal expansion (CTE) based materials. In wind and solar energy applications, IGBT’s reliability is highly influenced by the operating conditions such as variable wind speed and solar irradiance. Power losses occur in switching transient of high current/voltage which causes temperature fluctuations among the layers of the IGBTs. This is the main stress mechanism which accelerates deterioration and eventual failures among IGBT layers due to the dissimilar CTEs. Therefore, proper thermal monitoring is essential for accurate estimation of PECs reliability and end lifetime. Several thermal models have been proposed in literature, which are not capable of representing accurate temperature profiles among multichip IGBTs. These models are mostly derived from offline modelling approaches which cannot take operating conditions and control mechanisms of PECs into account and unable to represent actual heat path among each chip. This research offers an accurate and powerful electro thermal and reliability monitoring tool for such devices. Three-dimensional finite element (FE) IGBT models are implemented using COMSOL, by considering complex heat interactions among each layer. Based on the obtained thermal characteristics, electro thermal and thermo mechanical models were developed in SIMULINK to determine the thermal behaviour of each layer and provide total lifetime consumption analysis. The developed models were verified by real-time (RT) experiments using dSPACE environment. New materials, such as silicon carbide (SiC) devices, were found to exhibit approximately 20°C less thermal profile compared to conventional silicon IGBTs. For PECs used within wind energy systems, PECs driving algorithms were derived within the proposed models and by adjusting switching frequency PECs cycling temperatures were reduced by 12°C which led to a significant reduction in thermal stress; approximately 27 MPa. Total life consumption for the proposed method was calculated as 3.26x10-5 which is approximately 1x10-5 less compared to the other both methods. Effects of maximum power tracking algorithms, used in photovoltaic solar systems, on thermal stress were also explored. The converter’s thermal cycling was found approximately 3 °C higher with the IC algorithm. The steady state temperature was 52.7°C for the IC while it was 42.6 °C for P&O. In conclusion, IC algorithm offers more accurate tracking accuracy; however, this is on the expense of harsher thermal stress which has led to approximately 1.4 times of life consumption compared to P&O under specific operating conditions

On-line quality monitoring and lifetime prediction of thick Al wire bonds using signals obtained from ultrasonic generator

Abstract The reliable performance of power electronic modules has been a concern for many years due to their increased use in applications which demand high availability and longer lifetimes. Thick Al wire bonding is a key technique for providing interconnections in power electronic modules. Today, wire bond lift-off and heel cracking are often considered the most lifetime limiting factors of power electronic modules as a result of cyclic thermomechanical stresses. Therefore, it is important for power electronic packaging manufacturers to address this issue at the design stage and on the manufacturing line. Techniques for the non-destructive, real-time evaluation and control of wire bond quality have been proposed to detect defects in manufacture and predict reliability prior to in-service exposure. This approach has the potential to improve the accuracy of lifetime prediction for the manufactured product. In this thesis, a non-destructive technique for detecting bond quality by the application of a semi-supervised classification algorithm to process signals obtained from an ultrasonic generator is presented. Experimental tests verified that the classification method is capable of accurately predicting bond quality, indicated by bonded area as measured by X-ray tomography. Samples classified during bonding were subjected to both passive and active cycling and the distribution of bond life amongst the different classes analysed. It is demonstrated that the as-bonded quality classification is closely correlated with cycling life and can therefore be used as a non-destructive tool for monitoring bond quality and predicting useful service life

On-line quality monitoring and lifetime prediction of thick Al wire bonds using signals obtained from ultrasonic generator

Abstract The reliable performance of power electronic modules has been a concern for many years due to their increased use in applications which demand high availability and longer lifetimes. Thick Al wire bonding is a key technique for providing interconnections in power electronic modules. Today, wire bond lift-off and heel cracking are often considered the most lifetime limiting factors of power electronic modules as a result of cyclic thermomechanical stresses. Therefore, it is important for power electronic packaging manufacturers to address this issue at the design stage and on the manufacturing line. Techniques for the non-destructive, real-time evaluation and control of wire bond quality have been proposed to detect defects in manufacture and predict reliability prior to in-service exposure. This approach has the potential to improve the accuracy of lifetime prediction for the manufactured product. In this thesis, a non-destructive technique for detecting bond quality by the application of a semi-supervised classification algorithm to process signals obtained from an ultrasonic generator is presented. Experimental tests verified that the classification method is capable of accurately predicting bond quality, indicated by bonded area as measured by X-ray tomography. Samples classified during bonding were subjected to both passive and active cycling and the distribution of bond life amongst the different classes analysed. It is demonstrated that the as-bonded quality classification is closely correlated with cycling life and can therefore be used as a non-destructive tool for monitoring bond quality and predicting useful service life